Here are some questions I received recently regarding VLAN
tagging on the VIO server. My answers are shown in green.

“Hi Chris,

Q: I’m trying to
understand when, where and why there would be the need to use ‘mkvdev –vlan
(etc.) on the VIOS, and I’m wondering whether you would be able to clarify this
for me, please.

Is it necessary to add
the VLAN tag devices to the SEA, or is it suffice to just have them defined
within the Virtual Ethernet itself which is part of the SEA?”

A:
It is suffice to simply define the VLAN ids assigned to the Virtual Ethernet
adapters associated with the SEA.

“Q: For completeness,
on the rare occasions I have done this, I have added the VLAN’s to the Virtual
Ethernet and also as VLAN devices on the VIOS (mkvdev –vlan etc.)”

A:
mkvdev –vlan is not necessary, unless
the VIOS needs to communicate with hosts on different VLANs i.e. you need an IP
address on the VIOS for each VLAN. This does not mean the SEA will bridge this
VLAN traffic for VIOCs.

“Q: The reason I
started thinking of this is, is because one of our customers wants to add new
VLAN’s to their SEA, but they’re not running Power7 hardware. Therefore, the
online method would be to add a new Virtual Adapter which contains the new VLAN
ID’s to the VIOS using DLPAR, then use chdev –dev (etc.) on the SEA to include
the new Virtual Ethernet.”

A:
Agreed. The “IBM PowerVM Virtualization Managing and Monitoring” Redbook
states: “If your system doesn’t support dynamic VLAN modifications and you are
modifying the VLAN list of a virtual Ethernet adapter that is configured in a
SEA with ha_mode enabled, the HMC will not allow you to reconfigure the list of
VLANs on that interface. You will need to add an additional virtual Ethernet
adapter and modify the virt_adapters list of the SEA, or modify the profile of
both Virtual I/O Servers and re-activate both Virtual I/O Servers at the same
time.”

“Q: From the phone
call I had, it would appear that the VLAN tags are included on the Virtual
Ethernet device, but have not been added to the SEA by running mkvdev –vlan
(etc. ) on the VIOS’s. This leads me to assume that the ‘mkvdev –vlan’ is
only required if there is a requirement to access the VIOS itself from a
particular VLAN. Am I right, or is there something I’m not understanding?
I’m unable to find documentation that explains the answer. Do you happen to
know?”

A:
That is also my understanding (based on my experience). On page 483 of the “IBM
PowerVM Virtualization Introduction and Configuration” Redbook , it states:
“The addition of VLAN interfaces to the SEA adapter is only necessary if the VIO
Server itself needs to communicate on these VLANs”.

“Q: Hi Chris,

We are trying to
associate a new entX Virtual Ethernet Trunk Device to an existing SEA. The new
device must be configured for VLAN tagging. The existing virtual Ethernet
adapter that (is already associated with the SEA) is not configured for VLAN
tagging. This device will remain associated to the SEA and continue to pass
untagged packets to the already configured network.

Ultimately the configuration
we want would be two entX devices associated with the existing SEA. One entX
device is configured for notagged packets and the other entX device is
configured for tagging.

Reply: “hmm ok I see
what you are saying, I will give it a go and tell you how it turns out...thanks.
ok finally got around to testing using a VIOS at DR site. Created
new virtual adapter PVID 55 and VID 888 (ent9) then added it to the existing
SEA as shown below:

I was working
with a customer recently on a Power Blade that was running the Integrated
Virtualisation Manager (IVM). They’d installed a VIO partition onto the Blade
and had hoped to install a couple of AIX LPARs on the system. However they didn’t
get very far.

As soon as they
attempted to NIM install the LPARs, they would get stuck at trying to ping the
NIM master from the client. Basically, the Shared Ethernet Adapter (SEA) was
not working properly and none of the LPARs could communicate with the external
network. So they asked for some assistance.

The Blade server
name was Server-8406-71Y-SN06BF99Z. The SEA was configured as ent7.

On the network
switch port, the native VLAN (PVID), was configured as 11, with VLAN tag 68
added as an allowed VLAN. If the client LPARs tried to access the network using
a PVID of 68, instead of a VLAN TAG of 68, they would get stuck at the switch
port i.e. the un-tagged packets for 10.1.68.X via PVID 11 would fail. The
packets for 10.1.68.X needed to be tagged with VLAN id 68 in order for the
switch to pass the traffic.

So the question
was, how do we add VLAN tags in the IVM environment? If we’d been using a HMC,
then this would be simple to fix. Just add the VLAN tags into the Virtual
Ethernet Adapter used by the SEA and we’d be done.

We had to use the
lshwres and chhwres commands to resolve this one. First we listed the virtual
adapters known to the VIO server (IVM). At slot 12, we found our SEA adapter
with port_vlan_id set to 68 and addl_vlan_ids set to none.

We needed to
change port_vlan_id to 11 and addl_vlan_ids to 68. We also required
the ieee_virtual_eth value set to 1.

First we removed
the existing SEA adapter, as we would not be able to make changes to it while
it was “active”. We then removed the adapter from slot 12 and then re-added it,
again at slot 12, with port_vlan_id
and addl_vlan_ids set to the desired
values.